fix build with libressl >= 3.5.0

Fix the following build failure with libressl >= 3.5.0:

auth_priv.cpp: In member function 'virtual int Snmp_pp::AuthMD5::password_to_key(const unsigned char*, unsigned int, const unsigned char*, unsigned int, unsigned char*, unsigned int*)':
auth_priv.cpp:1132:20: error: aggregate 'Snmp_pp::MD5HashStateType md5_hash_state' has incomplete type and cannot be defined
   MD5HashStateType md5_hash_state;
                    ^~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/b50b883c03e82564198a8b7e91bd14bf007772e0

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Upstream status: merged (emailed to katz.agentpp.com@magenta.de)]

diff -Naurp snmp++-3.4.9.orig/src/auth_priv.cpp snmp++-3.4.9/src/auth_priv.cpp
--- snmp++-3.4.9.orig/src/auth_priv.cpp	2022-05-13 11:39:14.083038544 +0200
+++ snmp++-3.4.9/src/auth_priv.cpp	2022-05-13 15:00:42.576102348 +0200
@@ -79,8 +79,9 @@ static const char *loggerModuleName = "s
 
 /* -- START: Defines for OpenSSL -- */
 
-#if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
-// OpenSSL versions up to 1.0.x and LibreSSL
+#if OPENSSL_VERSION_NUMBER < 0x10100000L || \
+	(defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x30500000L)
+// OpenSSL versions up to 1.0.x and LibreSSL versions up to 3.4.x
 typedef EVP_MD_CTX            EVPHashStateType;
 
 int evpAllocAndInit(EVP_MD_CTX *ctx, const EVP_MD *md)
@@ -138,7 +139,7 @@ typedef EVP_MD_CTX*           MD5HashSta
 #define MD5_PROCESS(s, p, l)  EVP_DigestUpdate(*(s), p, l)
 #define MD5_DONE(s, k)        evpDigestFinalAndFree(s, k)
 
-#endif // OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
+#endif // OPENSSL_VERSION_NUMBER < 0x10100000L || (defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x30500000L)
 
 typedef DES_key_schedule      DESCBCType;
 #define DES_CBC_START_ENCRYPT(c, iv, k, kl, r, s) \